This invention relates to the art of processing communicated intelligence and has particular relationship to the evaluation of such intelligence for the purpose of identifying the characteristics of its source. The processing and evaluation with which this invention concerns itself is of unique interest in the evaluation of intelligence received from hostile radar systems, operating in an area, for the purpose of identifying these systems so that evasive action may be taken or countermeasures initiated.
Typically, it is contemplated that an aircraft carrying identifying apparatus (electronic countermeasure, ECM, devices) is operating in a region under surveillance of hostile radar which may include tracking (fire control) radar and scanning (search) radar. This craft must identify the radar and initiate countermeasures to preclude the location by the radar and destruction of other friendly craft in the area. It is essential that such identifying craft identify the parameters of the radar before the threat of destruction takes effect so that effective counteraction may be taken, both, to frustrate the threat and also to confuse or disrupt the reception of the radar. The identification of the radar and of its purposes must take place in a very short time interval to serve any useful purpose. Of particular importance is the necessity of evaluating the parameters received from the radar to determine if the radar is tracking radar since a craft under the surveillance of tracking radar may anticipate being immediately taken under fire.
Typical of the radar parameters which can serve for evaluation are:
1. Intensity of signal PA1 2. Carrier frequency PA1 3. DOA (direction of arrival) PA1 4. PRF (pulse repetition frequency) or PA1 Pri (pulse repetition interval) PA1 5. Pulse width PA1 6. Pulse shape PA1 7. Polarization PA1 8. RF phase.
a. elevation angle PA2 b. azimuthal angle
These parameters may inherently change, or may deliberately be changed, rapidly. DOA is inherently variable for an aircraft; carrier frequency is changed to avoid the effects of spot jammers; different pulse widths, pulse repetition frequencies, polarization or pulse shapes might be used against repeater jammers as in electronic counter countermeasure devices (ECCM).
In accordance with the teachings of the prior art, attempts have been made to carry out the identifying process with special purpose high speed computers programmed to give the data on the radars. These attempts have not yielded the high classification or identification rates required in a dense radar environment which is frequently encountered.
It is an object of this invention to overcome the disadvantages and disabilities of the prior art identifying apparatus and to provide radar-identifying apparatus and a method of radar identification which shall yield timely and reliable identification of radar under observation.